Safety relay for SIL 3 / Cat 4 circuits
The Siemens 3RK3251-1AA10 is a SIRIUS modular safety system rated SIL 3 per IEC 61508 and IEC 62061, and Category 4 per EN 954-1 and EN ISO 13849-1. That means it meets the highest single-fault-tolerant safety integrity level — suitable for guarding hazard zones where a single failure cannot lead to loss of the safety function. It carries 8 single-channel inputs and 4/8 F-RO (failsafe relay outputs), each rated 2 A at both 24 V DC and 230 V AC. The control supply is 24 V DC, and the insulation voltage is 300 V rated, with a surge withstand of 4 kV.
Snap-on DIN-rail mounting (vertical position only). Finger-safe touch protection (IP20) means it can sit in a control panel without additional cover over the terminals. Pollution degree 3 environment, so it tolerates conductive dust and condensation typical of industrial panels.